Segwit is the best possible update Bitcoin can have, followed later by a hf. After that sidechains, that will make Bitcoin mainstream.
Bitcoin is already mainstream.
And why is the hard fork may I ask? For the block size increase? Nobody will support that thing. If a hard fork happens to create a bigger block bitcoin, it will be an altcoin. They better start a new alt with the desired specs instead. They may even premine it till they
satisfy their greed! (Actually I don't think that's possible lol)